The invention relates to a method for estimating a movement of a subscriber terminal in a radio system comprising at least one base station and a subscriber terminal, at least one of which repeatedly measures and stores at different points of time a power of a received signal, the transmission power of the signal being substantially constant or known.
The invention also relates to a method for selecting a cell in a radio system comprising a plural number of microcells and at least one umbrella cell covering the microcells; the radio system comprising at least one base station and a subscriber terminal, which functions actively either in a microcell or an umbrella cell; and at least one base station or subscriber terminal repeatedly measuring and storing at different points of time a power of a received signal, the transmission power of the signal being substantially constant or known.
The invention further relates to a radio system comprising at least one base station and a subscriber terminal, at least one of which is arranged to repeatedly measure and store at different points of time a power of a received signal, the transmission power of the signal being substantially constant or known.
The invention also relates to a radio system comprising at least one base station and a subscriber terminal, which is arranged to function actively either in a microcell or an umbrella cell; at least one base station or subscriber terminal being arranged to repeatedly measure and store at different points of time a power of a received signal, the transmission power of the signal being substantially constant or known.
Various different methods have been developed for estimating the speed of subscriber terminals in a mobile system. Speed can be estimated on the basis of power measurements carried out, for instance, by observing quadratic changes in the power level of a received signal. With a suitable measurement period, the average of the changes correlates with the speed of the subscriber terminal. Such prior art solutions are typically based on the idea that an increase in speed causes increasingly bigger changes in the power level.
The measurement of speed can be applied for instance in a radio system in which one and the same area is covered both by a microcell network and a single large umbrella cell. In this case it is advantageous that high-speed subscriber terminals make a connection to an umbrella cell and low-speed subscriber terminals to a microcell network, otherwise the number of base station alternatives and disconnected calls increases.
A typical problem with prior art solutions is that since there is no clear interdependency between the extent of variations in power level and the speed of the subscriber terminal, particularly in a strongly varying environment, the determination of speed is unsuccessful. When speed cannot be determined, connection to a microcell or an umbrella cell cannot be optimally made either.
An object of the present invention is thus to provide a method and a radio system determining a speed of a subscriber terminal on the basis of variations in the power level of a received signal, without taking the extent of the variations into account. In addition, the making of a connection to microcells and umbrella cells by subscriber terminals is optimized on the basis of their speed.
This is achieved with a method described in the preamble, characterized in that measured powers of signals are used for producing a probability representing an interdependence between powers measured at least at two different points of time, the probability being used for estimating a movement of a subscriber terminal.
A method of the invention for selecting a cell in a radio system is characterized by using measured powers of signals for producing a probability representing an interdependence between powers measured at least at two different points of time, the probability being used for estimating a movement of a subscriber terminal; and selecting, on the basis of the estimated movement of the subscriber terminal, either a microcell or an umbrella cell as a cell for the active operation of the subscriber terminal.
A radio system of the invention is characterized in that the radio system is arranged to use measured powers of signals for producing a probability representing an interdependence between powers measured at least at two different points of time, the radio system being arranged to use the probability for estimating a movement of a subscriber terminal.
A radio system of the invention is also characterized in that the radio system is arranged to use measured signal powers for producing a probability representing an interdependence between powers measured at least at two different points of time, said probability estimating a movement of a subscriber terminal; the radio system being arranged to select, on the basis of the estimated movement of the subscriber terminal, either a microcell or an umbrella cell as a cell for the active operation of the subscriber terminal.
The invention provides considerable advantages. Subscriber terminal speed measured on the basis of a probability relating to a power level of a received signal allows speed to be more reliably determined, particularly in a varying environment. Also the location of a subscriber terminal in a cell hierarchy can be optimized and handover algorithms clarified.